Kinetic Energ...ammasun(2014)_Xin QUAN.pdf

Kinetic Energy Budgets during the Rapid Intensification ofTyphoon Rammasun(2014)Xin QUAN and Xiaofan LI*Key Laboratory of Geoscience Big Data and Deep Resource of Zhejiang Province,School of Earth Sciences,Zhejiang University,Hangzhou,Zhejiang 310027,China(Received 8 March 2022;revised 23 May 2022;accepted 30 May 2022)ABSTRACTIn this study,Typhoon Rammasun (2014)was simulated using the Weather Research and Forecasting model toexamine the kinetic energy during rapid intensification(RI).Budget analyses revealed that in the inner area of the typhoon,the conversion from symmetric divergent kinetic energy associated with the collocation of strong cyclonic circulation andinward flow led to an increase in the symmetric rotational kinetic energy in the lower troposphere.The increase in thesymmetric rotational kinetic energy in the mid and upper troposphere resulted from the upward transport of symmetricrotational kinetic energy from the lower troposphere.In the outer area,both typhoon and Earths rotation played equallyimportant roles in the conversion from symmetric divergent kinetic energy to symmetric rotational kinetic energy in thelower troposphere.The decrease in the symmetric rotational kinetic energy in the upper troposphere was caused by theconversion to asymmetric rotational kinetic energy through the collocation of symmetric tangential rotational winds and theradial advection of asymmetric tangential rotational winds by radial environmental winds.Key words:Typhoon Rammasun(2014),rapid intensification,kinetic energy budget,symmetric and asymmetric winds,divergent and rotational circulations,environmental flowsCitation:Quan,X.,and X.F.Li,2023:Kinetic energy budgets during the rapid intensification of Typhoon Rammasun(2014).Adv.Atmos.Sci.,40(1),7894,https:/doi.org/10.1007/s00376-022-2060-z.Article Highlights:The symmetric rotational kinetic energy in the troposphere increases during the rapid intensification of TyphoonRammasun.The increase in the lower troposphere results from the conversion of symmetric divergent kinetic energy via therotational-and divergent-flow interaction.The increase in the upper troposphere is due to transport of symmetric rotational kinetic energy from the lowertroposphere by strong upward motions.1.IntroductionTyphoons may experience a rapid intensification(RI)period before landfall,which often leads to large economiclosses and deaths in the coastal areas.For example,the maxi-mum wind speed in the super Typhoon Rammasun(2014),which is analyzed in this study,increased from 40 m s1 to60 m s1 within 24 h before landfall at Hainan,China on 18July2014,causing a huge economic loss of over 26 billionChinese Yuan and approximately 30 deaths.To effectivelyreduce the damage caused by typhoons,accurate typhoonforecasting is required to facilitate informed governmentaldecisions before landfall.When compared to the significantimprovement in the track forecasts of tropical cyclones(TC)in recent decades,improvement in TC intensity forecastshave shown relatively slower progress (Elsberry et al.,2007;Rappaport et al.,2009;DeMaria et al.,2014).The inten-sity forecasts mainly rely on numerical model guidance;how-ever,improvement of numerical predictions requires an in-depth understanding of the physical processes associatedwith the intensity change.Primary physical processes and fac-tors associated with TC intensity change include environmen-tal effects(DeMaria et al.,1993;Zeng et al.,2010;Feng etal.,2014),inner core dynamics(Montgomery and Kallen-bach,1997;Wang,2002;Miyamoto and Takemi,2015;Chen,2016;Chen et al.,2019),underlying surface forcing(Yang et al.,2008;Cheng et al.,2012;Cheng and Wu,*Corresponding author:Xiaofan LIEmail:xiaofanlizju.eduADVANCES IN ATMOSPHERIC SCIENCES,VOL.40,JANUARY 2023,7894 Original Paper Institute of Atmospheric Physics/Chinese Academy of Sciences,and Science Press and Springer-Verlag GmbH Germany,part of Springer Nature 20232020),and convection and latent heat release(Kanada andWada,2015;Li et al.,2016).Many studies have contributed to enhancing the under-standing of dynamic processes associated with the RI ofTCs.The RI of Hurricane Opal(1995)was caused by themean vertical advection and mean vorticity flux terms(Pers-ing et al.,2002).The RI of TC Dora(2007)was related tothe superposition of potential vorticity structure of thetrough with strong deformation(Leroux et al.,2013).TheRI of Typhoon Man-yi (2013)was associated with theenhanced mesovortex under the condition of reduced staticstability (Wada,2015).The RI of Typhoon Megi (2010)resulted from strengthened rotational circulations in the midand upper troposphere through the transport of vorticity(Chang and Wu,2017).The RI of Typhoon Vicente(2012)was largely affected by an upper-tropospheric “inverted”trough(Shieh et al.,2013).The analysis of the asymmetricimpacts at multiple scales during RI found that the changesin asymmetric circulations were associated with the baroclinicconversion from available potential to kinet